1. Field of the Invention
This invention relates generally to cement product making machinery and more particularly to a method and apparatus for high speed manufacturing of a wide variety of high quality products.
2. Description of the Prior Art
Prior art machines for forming concrete products include a product forming section comprising a stationary frame, an upper compression beam and a lower stripper beam. A mold box has a head assembly which is mounted on the compression beam, and a mold assembly which is mounted on the frame and receives concrete material from a feed drawer. A conveyer system feeds metal pallets to the product forming section.
The head assembly raises above the mold assembly when the compression beam moves vertically upward into a raised position. After the compression beam raises, the stripper beam raises thereby placing a pallet against a bottom side of the mold assembly. The pallet seals the bottom side of cavities in the mold assembly. The feed drawer moves concrete material over the top of the mold assembly and dispenses the material into the contoured cavities.
As the concrete material is dispensed, a vibration system shakes the mold assembly. The vibration system spreads the concrete material evenly within the mold assembly cavities to produce a more homogeneous concrete product.
After the concrete is dispensed into the mold cavities, the feed drawer retracts from over the top of the mold assembly. The compression beam lowers pushing shoes from the head assembly into corresponding cavities in the mold assembly. The shoes compress the concrete material. After compression is complete, the stripper beam lowers as the head assembly pushes further into the cavities against the molded material. A molded concrete product thereby emerges from the bottom of the mold assembly onto the pallet. The pallet then moves via conveyer from the product forming section.
Several problems occur with the above stated product forming process. As the vibrator system shakes the mold assembly, the rest of the product forming machine also shakes. Machine vibration tends to dampen vibration in the mold assembly. Thus, concrete material in the mold box does not spread evenly in the mold assembly. Machine vibration also fatigues machine parts and alters the clearances between the head assembly and mold assembly. Thus, machine and mold box operating life is reduced and product quality is limited and furthermore deteriorates with machine use.
Mold boxes of various sizes are constantly exchanged in the product forming machine to produce different product shapes. When a new mold box is mounted in the machine, the various moving parts of the machine such as attachments to the compression and stripper beams, must be realigned. Realignment is necessary so that the machine can properly engage mold boxes of different heights. The head assembly and the mold assembly must also be jimmied until properly aligned together. Thus, a significant amount of time is required to properly mount and align a new mold box in the product forming machine. Machine down time while changing mold boxes reduces overall product output.
Pallets are located in a receiving position under the mold assembly by pushing pallets end-to-end. Sliding the pallets into a receiving position incurs wear on the pallet and increases the overall cycle time of the machine. For example, the time required to push a pallet into the receiving position increases because the pallet speed must be slowed down as the pallet approaches the receiving position.
Further, as the feed drawer dispenses concrete material into the mold assembly, a certain amount of concrete material accumulates on the topside of the mold assembly. As concrete further accumulates on the front edge, concrete material begins to spill off a front edge of the mold assembly.
Accordingly, a need remains for a high output concrete product forming machine that produces a wide variety of high quality products.
It is, therefore, an object of the invention to increase vibration control in a cement product forming machine.
Another object of the invention is to reduce the amount of time required to mold cement products.
Another object of the invention is to increase the homogeneous consistency of cement products.
Yet another object of the invention is to reduce the amount of time required to exchange and align molds in a cement product forming machine.
An apparatus for forming concrete products comprises a frame for supporting various product forming components such as a vertically displaceable compression beam and a vertically displaceable stripper beam. A mold box having internal cavities contoured to define preselected product patterns is flexibly mounted to the frame. A feed drawer receives concrete material and dispenses the concrete material into the mold box cavities.
A vibration system vibrates the mold box without inducing any substantial vibration in the frame while at the same time reducing horizontal vibrational effects. The vibration system comprises a pair of spaced-apart, vertically extending vibrator rods connected at a top end to the mold box and at a bottom end to a drive means.
The drive means including a single drive shaft that actuates a vibrator unit that vibrates both the first and second vibrator rods while at the same time reducing frame vibration. The drive means also includes a gear box having a counter-rotating shaft for holding counter-weights. The shaft rotates the counter-weights offsetting vibration in the frame caused by the first and second vibrator units.
The mold box is mounted to the frame via spring steel plates. The plates are competed at opposite ends to the front and back sides of the frame. A center portion of the steel plates are coupled to the mold box via a vibration bracket. The vibration bracket includes a dowel that extends vertically up from a top surface to mate with a corresponding hole in the bottom of the mold box for automatically aligning the mold in a predetermined location in relation to the frame.
By reducing vibration in the frame and isolating vibration in the mold box, frame components are less likely to become misaligned. Thus, machine adjustments are preformed less often increasing the overall operating life of the product forming machine. The vibration system by reducing frame vibration also increases the effective mold box vibration in turn allowing concrete material to be spread more uniformly in the mold box.
The vibration system reduces vibration in the horizontal direction further reducing frame misalignments and at the same time allowing more precise mold box tolerances. For example, each mold box comprises a head assembly that inserts into a mold assembly. If the mold box is vibrated in a horizontal direction, the mold box assemblies must be spaced far enough apart so that the shoes on the head assembly do not bang against the internal cavities in the mold assembly. By reducing horizontal vibration, mold box assemblies can be designed to engage at closer distances allowing more detailed product designs and more effective compression and stripping processes creating higher quality concrete (e.g., blocks).
As previously mentioned, the mold box comprises a head assembly having multiple shoes that are insertable into associated cavities in a mold assembly. The mold box is mounted to the frame by bolting the head assembly to the compression beam and bolting the mold assembly to the frame. The novel alignment brackets lock the head assembly and the mold assembly into a predetermined aligned relationship. While the head assembly and mold assembly are bolted together, the mold box is then mounted to the frame. The alignment brackets allow the mold box to be mounted while maintaining the predetermined aligned position. After the alignment brackets are removed, the product forming machine moves the upper head assembly and the mold assembly in vertical directions up and down while maintaining the same predetermined aligned relationship.
The frame includes novel mounting means for mounting the mold box to the frame. The vibration bracket includes a shelf that holds the bottom side of the mold assembly in a predetermined position in relation to the frame. The bottom side mounting of the mold box allows alternative mold boxes having different heights to be attachable at the same predetermined positional relationship on the frame. Thus, the time required to exchange mold boxes is reduced.
The feed drawer assembly is held above the ground by telescoping legs each having an interior tube that is vertically displaceable inside an associated exterior tube. Jack screws attached to the feed drawer assembly move the inner tube of each telescoping leg up and down. A drive motor synchronously rotates each jack screw in the same direction and at the same speed thereby controlling vertical displacement of the feed drawer assembly.
Air-bag activated locks are used to lock each telescoping leg into a given vertical position transferring weight from the jack screws. Each air lock includes a puck that extends through a hole in the exterior tube. When the air-bag actuates, the puck clamps against the inner tube locking the telescoping leg in a given vertical position.
The feed drawer assembly includes a brush that removes concrete material from the head assembly shoes while the compression beam is in a raised position. The feed drawer also includes a horizontally displaceable wiper blade that scrapes concrete material from the top of the mold assembly into the internal cavities of the mold assembly. The wiper blade prevents concrete material from accumulating and falling off the front edge of the mold box.
The concrete products are formed and carried on metal pallets. The concrete block forming machine includes a pallet feeder that individually moves the pallets in a unitized fashion underneath the mold box. The pallet feeder includes an infeed rack for locating pallets under the mold box and an outfeed rack, located adjacent to the infeed rack, for moving the pallets from underneath the mold box to a conveyer. An arm pivotally coupled to the frame slides the pallet feeder back and fourth. The arm oscillates back and forth in a 180 degree rotation about a vertically aligned axis.
A vertically displaceable conveyer transfers pallets onto the pallet feeder infeed rack. The stripper beam then lifts the pallets from the infeed rack to a position up against the underside of the mold assembly. After concrete products have been formed and placed on the pallet, the stripper beam lowers the pallet down onto the outfeed rack. The outfeed rack then removes the pallet from under the mold box.
The pallet feeder allows pallets to be moved quickly into position underneath the mold box reducing the overall cycle time of the concrete product forming machine. By carrying pallets both underneath and away from the mold box, the machine precisely controls pallet positioning. Carrying the pallets also reduces pallet wear over systems that simply push pallets underneath the mold box.
The compression beam and the stripper beam are operated together and separately to reduce overall machine cycle time and to increase the quality of the formed products. The novel hydraulic piston operation ensures that both the compression and stripper beams move at precise speeds in relation to each other.
The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention which proceeds with reference to the accompanying drawings.